Elna Stongs teaches practical combat skills to S-Class students at the Hero Academy, a position she assumed one year before the series begins. Her prior background spans seventeen years as a mercenary, starting at age seven and concluding at twenty-four, granting her extensive combat experience. This history informs her formidable combat prowess and philosophy of achieving victory by any means necessary.

Her teaching methods are exceptionally strict, surpassing typical harsh instructors. Elna possesses keen insight for assessing students' physical capabilities. With male students who meet specific conditions or exceed expectations, she leverages her physical appeal as motivation, offering rewards like sitting on them or grinding against them—actions stemming from her shameless willingness to use her sexuality for engagement.

Physically, Elna has black hair, black eyes, and an H-cup figure, contributing to her student appeal. She maintains a cool-headed demeanor but leads an undisciplined lifestyle, including habits like extorting students' savings. She frequently suffers from stiff shoulders, accepting massages from Noir Stardia in exchange for providing him rewards or information due to the relief he offers.

Her combat skills are diverse, encompassing swordsmanship, martial arts, earth-elemental abilities, and healing magic, reflecting her mercenary background and practical instruction style. During a hot spring incident, she fought alongside Noir against students attempting to spy on bathing women, demonstrating her willingness to engage physically when circumstances align with her judgment.

Elna occupies a distinct position relative to other female characters associated with Noir Stardia. She blends tomboy and "onee-san" (older sister) archetypes, acting as an older role model while exhibiting spunky, independent, and physically powerful traits, contrasting with more servile personalities. Though unofficially considered part of Noir's harem, she lacks the devotion shown by others. She remains a free spirit, acknowledging Noir's capabilities and occasionally acquiescing to his requests without forming deeper emotional ties. While her screen time is less than other heroines, her presence commands attention during appearances.